To examine the influence of repeated bouts of exercise on the GH response to exercise, 20 healthy young men and women will exercise (at the lactate threshold) for 30 min. on a bicycle ergometer at 3 times during the day. Blood samples will be obtained for 24 h at 5-10 min intervals. There will be a control admission (no exercise), a sequential exercise admission (1000,1130,1300) and a delayed exercise admission (1000, 1400, 1800). Subjects will receive standard meals at 0600 and 2200 h. No additional subjects are being entered in this study. All data have been collected. We have been analyzing data and waiting for assayed data to become available. COMPUTER LAB ONLY.